The Obsidian dagger - Catherine Webb

There seem to be some odd things going on in the city of London, lately. Take the murders, for instance; quite peculiar. And those missing statues - what's going on there? And shouldn't Saint Paul's have a roof? Odd. . .

Horatio Lyle, of course, is no stranger to. . . well, strangeness.
In fact, he finds the lure of the unknown quite invigorating. But having just survived the most frightening episode in his life, the last thing he wants is that pompous Lord Lincoln sticking his nose in again and demanding that he take on another case the police are too thick to solve. Of course, His Lordship can be painfully persuasive at times, so it should come as no surprise that Lyle, along with his young proteges Tess (the thief) and Thomas (the toff),
and his faithful hound Tate (the smart one), is soon up to his cravat in events of a singularly unscientific nature.

Actually, it would all
be terribly exciting if only they weren't trying to kill him.